There is known a corrugated tube with a slit, which is fitted on a wire harness to protect the same, and is installed (see, for example, Patent Literature 1).
As shown in FIGS. 13A and 13B, the corrugated tube 100 is made of a synthetic resin, and has a bellows-like cylindrical shape, and has annular root portions (smaller-diameter portions) 101 and annular ridge portions (larger-diameter portions) 102 arranged alternately at the same pitch in an axial direction, and the slit 103 is formed in the axial direction over an entire length thereof to provide a cut-shape.
Therefore, when such a corrugated tube 100 is to be fitted on a wire harness installed in an automobile, the corrugated tube is fitted on the wire harness laterally of the axial direction, using the slit 103 as an opening. Then, in some cases, an adhesive tape is roughly wound on an outer surface of the corrugated tube 100 to prevent the slit 103 from being opened. When the corrugated tube 100, receiving the wire harness therein, is to be installed, it is common to install the corrugated tube in such a manner that the slit 103 is disposed in the vicinity of a lowermost point so that water, intruding into the inside of the corrugated tube 100, and condensation water can be discharged through the slit 103.
Also, there is known an apparatus for forming a slit in a tube (see, for example, Patent Literature 2). FIG. 14 is a schematic perspective view showing a tube-slit forming apparatus disclosed in Patent Literature 2.
As shown in FIG. 14, in the tube-slit forming apparatus 110, the tube 111 is guided in an expanded manner by a rod-like member 112 passing through the tube 111, and is pushed out toward a cutter 114 by rotation of rollers 113, and a slit (not shown) is formed in the tube 111 by the cutter 114. Thus, the straight slit can be easily formed in the tube 111.    Patent Literature 1: JP-A-2003-309918 Publication (FIG. 3)    Patent Literature 2: JP-A-2001-260072 Publication (Pages 2 to 3, FIG. 1)